Satellites produce new ultra-precise topographic map of Earth

German satellites TanDEM-X and TerraSAR-X spent five years orbiting Earth in close formation to create 3D global map of unprecedented accuracy

A colour-coded terrain model of a region of Northeast Greenland National Park, with the Elephant Foot Glacier visible in the centre. Topographical data captured by the TanDEM-X satellite is so precise, glacial movements can be measured in centimetres, and changes in elevation caused by melting ice can be measured in metres. (Image: German Aerospace Centre - DLR)

Geographers around the world have a powerful new tool at their disposal: the most accurate large-scale topographical map of Earth's surface ever created.

Two German-built satellites, TanDEM-X and TerraSAR-X, spent five years orbiting the planet in extremely close formation, repeatedly scanning Earth's land masses with powerful radar sensors.

The satellites beamed some 500 terabytes of data back to Earth, where remote sensing specialists at the German Aerospace Centre (DLR) processed it to create elevation maps of unprecedented detail — sometimes accurate to within one metre. Prior to the TanDEM-X mission, elevation models for large parts of Earth were low resolution, inconsistent or incomplete.

The database, which is available for free to researchers, is already proving a boon to scientists studying the effects of climate change: glacial movements can be measured in centimetres, while ice elevation loss or gain can be measured in metres.

"Using the current elevation model, we have shown that in some regions of Earth, glaciers are losing up to 30 metres in thickness per year in the area of the glacier tongues," says Richard Baumler, director of DLR's Remote Sensing Technology Institute.

The twin satellites still have some years of life left, so DLR has proposed another mission that would see them produce a new 3D map of Earth every eight days, albeit in less detail. This would allow researchers to track changes in Earth's topography over time — for example, the impacts of natural disasters or the loss of forested areas.